Electric vehicles with or without a supplemental IC engine (i.e., hybrid electric vehicle) require onboard batteries to power their electric drive systems. The performance requirements of electric vehicles dictate the need for ganging many batteries together into a variety of configurations depending on the vehicle's design. Batteries so ganged together are known as a battery pack. A battery pack comprises a plurality of individual batteries electrically connected one to the other, is anchored to the vehicle and will typically include a number of accessory electronic components for controlling the charge and discharge performance of the pack. The problems associated with packaging and positioning of a large mass within the vehicle becomes even more complicated when the vehicle design necessitates that the batteries be stacked or tiered on top of each other as is often required to maximize energy storage potential while minimizing space utilization within the vehicle. The battery pack can approach 50 percent of the vehicle's weight especially when the batteries are of the lead-acid variety. In some cases so many batteries are required to satisfy a vehicle's power demands that layers of batteries are tiered one atop the other in a stack and these many batteries must be securely retained in both the horizontal and vertical directions for minimizing dynamic effects on the vehicle. Due to the size and mass of the battery packs, the structural ramifications to the vehicle are considerable and the battery pack's location and configuration has a direct and significant impact on the ride, handling, and performance of the vehicle. The manner in which the batteries are packaged and retained in the vehicle are so crucial to the function of the vehicle that ofttimes the battery pack forms a structural part of the vehicle. The hold-down devices for the batteries must be lightweight yet adequate to minimize any movement of the batteries in the pack. The stacking/tiering of batteries introduces several problems that must be considered in the battery pack hold-down system. The batteries must be firmly held vertically for elimination of bounce and associated noise while at the same time also must be held horizontally to minimize dynamic affects on the vehicle's handling. At the same time, it is necessary to minimize the weight of the hold-down system so that the performance and the range of the vehicle is not unnecessarily compromised. Finally due to the material used to form the battery cases (i.e., typically injection molded polypropylene), batteries have tendencies to creep away from pressure points introduced with the hold-down fastening systems commonly seen today, e.g., for SLI applications resulting in a loosening of the batteries in the pack and consequent movement thereof in the vehicle.
It is a principal object of the present invention to package an electric vehicle battery pack, stacked or unstacked, in such a way that the batteries remain tightly packed and environmentally sealed, the packaging contributes to the structural integrity of the vehicle, and the pack is not a detriment to the vehicle's performance. It is a further object of the present invention to provide a packaging scheme with minimal fasteners and parts which allows considerable design flexibility for a variety of battery pack configurations. These and other objects and advantages of the present invention will become more readily apparent from the description thereof which follows.